Human skin comprises three principal layers: the epidermis, the dermis, and the subcutaneous fat layer. The epidermis comprises four layers (from external to internal): the stratum corneum, the granular layer, the spiny layer, and the basal layer. A separate fifth layer, the stratum lucidum, may be present between the stratum corneum and granular layer. The basal layer produces cells which gradually migrate outward to form the other epidermal layers. As these cells migrate outward, they lose their central nucleus and start to produce skin proteins (keratins) and fats (lipids). These cells are identified as keratinocytes when present in the upper layers of the epidermis. Melanocytes are another class of cells located in the basal layer of the epidermis. Melanocytes are responsible for the production of melanin, which is primary factor in skin pigmentation.
Melanin is produced by a complex set of reactions within the melanocyte involving, at a basic level, the enzyme tyrosinase and L-tyrosine as a substrate. Tyrosinase catalyzes the conversion of L-tyrosine to DOPA (L-3,4-dihydroxyphenylalanine) and of DOPA to dopaquinone. Dopaquinone undergoes further conversion to form melanin. Melanin aggregates in organelles known as the melanosomes which are transferred to keratinocytes along slender filaments of the melanocyte known as dendrites. There are approximately 1500 gene products expressed in melanosomes with 600 of them being expressed at any given time and 100 of them believed to be unique to the melanosome. In addition, there are many regulatory elements involved in signaling, in the transport of melanosomes within the melanocyte, and in the transfer of melanosomes to the keratinocytes.
The production of melanin can be triggered by a variety of external and internal events. For example, melanocytes produce additional melanin when skin is subjected to UV radiation. The melanin is then transported via melanasomes to the keratinocytes, which then leaves the skin with a pigmented or “tanned” appearance. However, chronic UV exposure may lead to more subtle changes in skin tone. Often these changes are described as uneven tone or as a mottled appearance. Moreover, inflammation-related skin disorders such as atopic dermatitis or post-inflammatory hypopigmentation can also leave the skin with uneven tone appearance.
On the other hand, melanin is able to absorb electromagnetic irradiation especially the wavelengths of UV radiation. Furthermore, melanin acts as a scavenger for radicals. Thus, melanin is generally considered as a natural skin filter for UV radiation. Thus, there is a desire to provide compositions and methods of treatment that can improve the appearance of unevenly toned skin and provide a uniformly tanned appearance, which may provide an aesthetic benefit (e.g., perceived younger appearance than chronological age) in addition to providing protection against UV radiation-induced skin damage.
Over recent years, consumers have increasingly demanded “natural” cosmetic products. As a result, cosmetic manufacturers have incorporated more plant-based materials into their cosmetic formulations. Although various plants have been used for hundreds or even thousands of years for a variety of reputed indications, until recent times it has not been possible to clinically verify purported effectiveness or to identify new potential uses based upon the underlying science of the plant's bioactivity. With recent advances in science, researchers are now better able to assess the efficacy and/or potential new uses for plants that until recently were only supported by folklore. Because of the newness of the science, and because the number of plants that could potentially be utilized as cosmetic bioactives is so immense, the vast majority of plants have not yet been fully investigated.
Many of the methods used for extracting botanical components from plants involve techniques that are harmful to the plant tissue composition and/or the bioactive components of interest contained in that tissue. Consequently, traditional extraction methods often fail to deliver the full spectrum of activities that exist within a plant cell and thus the full potential of botanical-based cosmetic formulations is not realized. In addition, many traditional extraction methods utilize harsh chemical solvents, which are not “natural” and thus are materials that consumers want to avoid applying to their skin. Furthermore, these solvent-based processes produce toxic chemical wastes that can harm the environment if not properly handled and disposed of as hazardous waste.
Moreover, just because a material is “natural” does not guarantee that it is free from undesired substances that would make the material suitable for use on skin, however. For example, many plants contain photosensitizers such as pheophorbides and/or contact allergens such as proteins. At levels naturally found in many common plants, pheophorbides and/or proteins do not cause concern for most people. However, when plant materials are condensed to a highly concentrated form, such as through extraction, these materials can be present at levels that cause skin irritation and allergic reactions, including rashes. Even when these materials are present at their natural levels, however, there are still many sensitive individuals who experience negative skin reactions.
Furthermore, as demands for natural products have increased, so have concerns about protecting earth's natural resources. Many of the “natural” ingredients that consumers desire are derived from bioresources that are depleted and/or destroyed when harvested for use in consumer products. Thus, consumers' desire for natural, more earth-friendly products can ironically lead to the destruction of the very bioresources they aim to preserve.
Thus, there is a need for natural bioactive botanical compositions that maintain their spectrum of desired bioactivity, are suitable for topical skin application, and are not prepared using harsh chemical solvents. Furthermore, there is a need for cosmetic compositions containing such bioactives that are effective for improving the appearance of skin pigmentation. In addition, there is a need for such bioactive materials that can be harvested and processed in an ecologically sound, sustainable manner.
These and other objects of the present invention will become apparent in light of the following disclosure.